Conventional storage of whole blood is accompanied by the accumulation of microaggregates in blood which are thought to be harmful when transfused (pulmonary microembolism). This particulate matter derives principally from dead or disintegrating white blood cells and platelets which have a much shorter life (3 to 5 days) than oxygen-carrying red cells. Non-viable platelets and leucocytes are unnecessary in the context of stored-blood transfusion. Current transfusion practice relies upon microfiltration of this debris between the container and the patient during the process of transfusion for removal of this solid matter. This is a moderately expensive and imprecise procedure. Moreover, failure to remove this debris completely can have serious consequences.
As an example of such consequences, febrile reactions and sensitivity to transfused blood are frequently related to transfused white blood cells or platelets which are non-functional after storage. Current methodology for their total removal from transfused blood is time-consuming, relatively costly and cumbersome and wasteful of up to 25% of the red cell mass.
A further point to be considered is that not all patients require whole blood transfusion. Many patients specifically require only plasma, red cells, white cells or platelets. Hence, fractions from any given unit ideally should be capable of serving more than one patient if necessary. Although current component methodology for this purpose is relatively well-defined, separation of components is usually irreversible once it is performed.
A number of attempts have been made to overcome the difficulties described above, one such attempt being described by W. C. James in U.S. Pat. No. 3,513,976.
James shows two rigid flasks, each having a conical end, the conical ends being joined by a neck. The objective of this device is similar to that of subject invention, namely a device which can be subjected to settling in order to establish interfaces which lie within the neck; adjustment can be made by adding mercury to the bottom flask through a tube or by removing mercury originally present from the bottom flask. The separated white cells or plasma can then be removed through a pipette. Clearly, this is an undesirable method because of inevitable admixture during pipetting, breach of sterile technique in blood handling and the obvious hazards of mercury contact. Although not so stated in the patent, it is evident that James' flasks are rigid; at column 2, line 50, it is stated that the device may be made of glass or any other material having the required property of transparency. This description could include a transparent plastic film, but the entire description reads in general on a rigid structure.
G. R. Ryan in U.S. Pat. No. 3,761,408 shows a flexible plastic bag in a transfusion apparatus. In his FIG. 9 the bag is shown separated into two portions by clamps, so that plasma and cells can be withdrawn separately. In addition, in column 3, line 5 and 6, Ryan states that heat sealing may be used instead of the clamps. (1) However, white blood cells and platelets cannot be immediately and aseptically segregated or removed from blood; (2) blood components cannot be either stored in or transfused directly from individual parent chambers to patient; (3) the option for component or whole blood therapy cannot be maintained throughout the period of blood storage and (4) the capacity for in-container washing is not afforded.
As is evident, although the concept of a plastic bag for use in the separation of whole blood has been disclosed and the concept of a design which facilitates separation of the components has also been disclosed, although with respect to rigid apparatus, it would be highly desirable that there be made available a plastic bag which is low in cost and which can be subjected to centrifugation to facilitate separation of various components. Moreover, the design of the bag should be such as to make it possible to recover virtually the entire quantities of red blood cells in the original volume of blood. Further, the design should be such that any of the components can be taken off separately, the components referred to being plasma, buffy coat with platelets, and packed red cells, and that, where desired, red blood cells in combination with plasma can be obtained. Finally, the design should be such that microfiltration for the purpose of removal of debris from the separated products should not be necessary.